<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="jquery-3.2.1.min.js"></script>
    <script>
        // window.onload = function () {}
        $(function () {
            //$("#mySpan") 得到id为mySpan的元素对象
            //html() 得到元素标签中间的内容，相当于innerHTML
            // alert($("#mySpan").html());

            //html("123d") 设置元素标签中间的内容
            // $("#mySpan").html("123d")


        })
    </script>
</head>
<body>
    <span id="mySpan">abc</span>
</body>
</html>